1. Field of Invention
The present invention relates to a power tool with an oil circulation apparatus.
2. Related Prior Art
Referring to FIG. 7, a conventional power tool 110 includes a sleeve 120, a bearing 128, a ball 127, a converter 130, two pistons 150, a retaining ring 140, a striker 160 and a spring 170. The sleeve 120 includes an aperture 121, a small space 123 communicated with the aperture 121 and a large space 125 communicated with the small space 123. A recess 126 is defined in the wall of the small space 123. Two grooves 122 are defined in the wall of the large space 125. The bearing 128 is put in the small space 123. The ball 127 is put in the recess 126. The ball 127 slides on the bearing 128. The converter 130 is an annular element and includes an annular cam 134 formed with an inclined edge, an annular rib 133 formed on the annular cam 134 and teeth 135 formed on an internal face. Each piston 150 includes an annular groove 152 for receiving the annular rib 133. The converter 130 is put in the large space 125 so that the pistons 150 are put in the grooves 122. The annular retainer 140 includes two recesses 142 defined in the periphery thereof. The annular retainer 140 is put in the large space 125 so that the recesses 142 receive the pistons 150. The spring 170 is put in the large space 125 and inserted through the annular retainer 140. The striker 160 includes teeth 162 formed on a first section, two tabs 164 formed on a second section next to the first section and a square insert 165 formed on a third section next to the second section. The teeth 162 are engaged with the teeth 135. The spring 170 is compressed between the tabs 164 and the annular rib 133. In operation, the sleeve 120 is rotated. The ball 127 is rotated together with the sleeve 120. The inclined edge of the annular cam 134 is pushed by the ball 127. Thus, the rotation of the ball 127 is converted to rectilinear movement of the annular cam 134. The pistons 150 are moved by the annular rib 133. The tabs 164 are pushed by the pistons 150. Thus, the striker 160 is moved. Lubrication for reducing the friction between the elements is important. To this end, oil is filled in the sleeve 120. However, oil is expelled from the sleeve 120 easily when the pistons 150 and the tabs 164 are moved towards the exterior of the sleeve 120. The friction between the elements thus rises so that the elements wear out one another.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in the prior art.